Book/Report

FZJ-2016-05225

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Quantitative Mikrosondenuntersuchungen zur Oxidation von Hochtemperaturlegierungen bei niedrigen Sauerstoffpotentialen

Maldonado Lopez, L. A. (Corresponding author)FZJ* ; Grübmeier, H.FZJ* ; Naoumidis, A.FZJ* ; Nickel, H.FZJ*

1987
Kernforschungsanlage Jülich GmbH, Zentralbiliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/12501

Report No.: Juel-2120

Abstract: Using electron probe microanalysis techniques, the oxidation of two high temperature alloys (Alloy 617 and Alloy 800 H) has been investigated. Specimens were exposed for up to 5000 h in a simulated methane reformer gas environment in the temperature range 800 to 950°C. Oxygen partial pressures were in the range 10$^{-19}$ to 10$^{-16}$ bar. In the investigation, particular attention was given to the determination of quantitative data for the oxide scales formed at the surface, the analysis of minor elements in the scale and the depletion effects in the matrix immediately below the scale. The oxide scale formed on Alloy 800H was found to comprise two layers, an outer layer containing Mn$_{(1+x)}$Cr$_{2(1-x)}$ Ti$_{x}$O$_{4}$ (spinel) and MnTiO$_{3}$ (Ilmenite type) and an inner layer of Cr$_{2-y}$Ti$_{y}$O$_{3}$ where 0.05 < y < 0.07. The specimens of Alloy 617 formed mainly single pnase scales consisting of Cr$_{2-y}$Ti$_{y}$O$_{3}$. Concentration profiles in the sub-surface regions for the constituent elements were measured and used to determine the mass flow at the surface in mg cm$^{-2}$. The mass flow was then incorporated as a boundary condition in a diffusion program for calculation of the concentration profile. The program allowed derivation of the diffusion coefficients of Cr, Mn and Ti, and the values obtained were in good agreement with those published in the literature. It was found that the dissolution of chromium carbides in the near-surface regions caused by depletion of chromium to form the scale contributed up to 50 % of the chromium consumed in oxidation in Alloy 617. In Alloy 800 H, the contribution was significantly lower.

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Contributing Institute(s):

1. Publikationen vor 2000 (PRE-2000 ; Retrocat)

Research Program(s):

1. 899 - ohne Topic (POF3-899) (POF3-899)

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